On Sun, 7 Jul 2019 12:19:01 +0100, Gareth's was W7 now W10 Downstairs
Computer wrote:

Clearly, the nuts on the fittings need to be nipped up
again, but is the greenness indicative of a high rate of
corrosion in the system due to the salt, or is it just
a reaction to the air once it had seeped?

Water softeners do not introduce salt (NaCl) into the water pipework.